This invention relates generally to catheters, and more particularly, to a catheter with a composite stiffener.
Catheters are increasingly used to access remote regions of the human body and, in doing so, delivering diagnostic or therapeutic agents to those sites. In particular, catheters which use the circulatory system as the pathway to these treatment sites are especially practical. Catheters are also used to access other regions of the body, e.g., genito-urinary regions, for a variety of therapeutic and diagnostic reasons. One such treatment of diseases of the circulatory system is via angioplasty (PTA). Such a procedure uses catheters having balloons on their distal tips. It is similarly common that those catheters are used to deliver a radiopaque agent to the site in question prior to the PTA procedure to view the problem prior to treatment.
Often the target which one desires to access by catheter is within a soft tissue such as the liver or the brain. These are difficult sites to reach. The catheter must be introduced through a large artery such as those found in the groin or in the neck and then be passed through ever-narrower regions of the vascular system until the catheter reaches the selected site. Often such pathways will wind back upon themselves in a multi-looped path. These catheters are difficult to design and to utilize in that they must be fairly stiff at their proximal end so to allow the pushing and manipulation of the catheter as it progresses through the body, and yet must be sufficiently flexible at the distal end to allow passage of the catheter tip through the loops and increasingly smaller blood vessels mentioned above and yet at the same time not cause significant trauma to the blood vessel or to the surrounding tissue. Further details on the problems and an early, but yet effective, way of designing a catheter for such a traversal may be found in U.S. Pat. No. 4,739,768, to Engelson. These catheters are designed to be used with a guidewire. A guidewire is simply a wire, typically of very sophisticated design, which is the xe2x80x9cscoutxe2x80x9d for the catheter. The catheter fits over and slides along the guidewire as it passes through the vasculature. Said another way, the guidewire is used to select the proper path through the vasculature with the urging of the attending physician and the catheter slides along behind once the proper path is established.
There are other ways of causing a catheter to proceed through the human vasculature to a selected site, but a guidewire-aided catheter is considered to be both quite quick and somewhat more accurate than the other procedures. One such alternative procedure is the use of a flow-directed catheter.
This invention is an adaptable one and may be used in a variety of catheter formats. The construction technique has the benefit of producing catheter sections having small overall diameters but with exceptional strength, resistance to kinking, and recovery from kinking (even in vivo) should such kinking occur. The catheter may be used in conjunction with a guidewire, but the catheter may also be used as a flow-directed catheter with the attachment of a balloon or in combination with a specifically flexible tip.
The use of a braid or coil in a catheter body is not a novel concept. Typical background patents are discussed below. However, none of these documents have used the concept of this invention to produce a catheter having the structure and physical capabilities of the catheter of this invention.
U.S. Pat. No. 5,454,795 discloses a kink-free spiral wound catheter. The catheter includes a stiffener ribbon, typically metallic, spirally wound within the catheter body to create a catheter having controllable stiffness. The stiffener is included in a distal section of the catheter.
U.S. Pat. No. 5,702,373 shows a catheter having a reinforced braid typically of superelastic alloy ribbon located in a distal section of the catheter. The superelastic alloy ribbon provides high resistance to kinking.
This invention is a catheter having a) a more proximal section preferably made up of an inner tubular liner, a first stiffener comprising a metal alloy, and a second stiffener comprising a non-metal alloy, the first and second stiffeners being coaxially wound exterior to the proximal inner liner; and b) a more distal section comprising a distal inner tubular liner, and the second stiffener coaxially wound exterior to the distal inner liner. The first stiffener desirably terminates before reaching the distal section to provide a more flexible distal section. Other sections of these or other designs may be placed variously between the noted sections or distal of the distal section described above.
The stiffeners may be wound in a number of different ways. For example, the stiffener may comprise a single strand of ribbon wound in a single direction or multiple strands interwoven in a braid. The first and second stiffeners may be independently wound as a coil or braid or may be interwoven to form a single braid. The first stiffener may include ribbons formed of a superelastic alloy such as nitinol, for example. The metal stiffener provides kink resistance to the proximal section of the catheter. The second stiffener may include a polymer such as liquid crystal polymer, polyurethane, polyimide, polyethylene, polyethylene terephthalate, or Nylon, for example. The second stiffener is desirably made from a material which is capable of being permanently deformed when exposed to steam so that the catheter may be shaped to have various bends for a specific surgical procedure.
The catheter may also have an outer cover exterior to the stiffener. The inner tubular liner and outer cover may be of a polymeric composition. A lubricious coating may be applied to the outer surface of the outer cover or the inner surface of the inner liner.
The catheter assembly may also have such ancillary components as a luer-lock and some manner of providing radiopacity.
The above is a brief description of some deficiencies in the prior art and advantages of the present invention. Other features, advantages, and embodiments of the invention will be apparent to those skilled in the art from the following description, drawings and claims.